Phenylalanine analyses of blood-spot control materials: preparation of samples and evaluation of interlaboratory performance.
Abstract Aliquots (0.1 mL) of whole-blood pools prepared to contain various concentrations of phenylalanine were applied to filter-paper collection cards, dried, and stored in sealed bags. We measured the phenylalanine content of the dried blood spots by bioassay, fluorometry, and "high-performance" liquid chromatography, and found that the concentrations remained constant for two years when samples were kept at -20 degrees C or lower. Intra- and interlaboratory studies showed that results for phenylalanine were greater for laboratories using bioassay procedures than for those using fluorometric procedures. Further, CVs (both among- and within-laboratory) obtained with fluorometric procedures were nearly half as great as the CVs obtained by laboratories using bioassay techniques.
Fluorometric determination of sisomicin, an aminoglycoside antibiotic, in dried blood spots on filter paper by reversed-phase high-performance liquid chromatography with pre-column derivatization.